1. Field of the Invention
The present method relates to determination of the portion of the breast cancer genome common to many patients with normal inheritance and expression patterns for targeting pharmaceutical treatments. The method identifies drug targets for approved drugs and others in development and the sequences of these targets can be used to prioritize the selection of one or more drugs used in combination chemotherapy.
2. Description of the Related Art
Mutation studies establish which essential gene products are critical for growth and development of tumors. Despite extensive genomic instability, presumably, a minimal set of gene products are required for tumor cell survival. Loss-of-function mutations required for the proliferation and survival of cancer cells have been investigated using RNA interference. Ngo V N, Davis R E, Lamy L, Yu X, Zhao H, Lenz G, Lam L T, Dave S, Yang L, Powell J and others. 2006. A loss-of-function RNA interference screen for molecular targets in cancer. Nature 441:106-10; Silva J M, Marran K, Parker J S, Silva J, Golding M, Schlabach M R, Elledge S J, Hannon G J, Chang K. 2008. Profiling essential genes in human mammary cells by multiplex RNAi screening. Science 319:617-20.
Functional genetic analyses have identified causal cancer genes and much effort has been made to determine their contribution to the tumorigenic phenotype. Human cancers arise from the accumulation of numerous genetic and epigenetic alterations, which lead to dysregulation of protein-coding genes and interacting genes within a pathway. Schafer M, Schwender H, Merk S, Haferlach C, lckstadt K, Dugas M. 2009. Integrated analysis of copy number alterations and gene expression: a bivariate assessment of equally directed abnormalities. Bioinformatics 25:3228-35. Microarray studies assess abnormalities in copy number of specific genes, novel patterns of genome rearrangement and their association with survival in breast cancer, expression, and methylation status. Widschwendter and Jones, 2002. Hicks J, Krasnitz A, Lakshmi B, Navin N E, Riggs M, Leibu E, Esposito D, Alexander J, Troge J, Grubor V and others. 2006. Genome Res 16:1465-79. Perou C M, Sorlie T, Eisen M B, van de Rijn M, Jeffrey S S, Rees C A, Pollack J R, Ross D T, Johnsen H, Akslen L A and others. 2000. Molecular portraits of human breast tumors. Nature 406:747-52. Feinberg A P, Tycko B. 2004. The history of cancer epigenetics. Nat Rev Cancer 4:143-53. Widschwendter M, Jones P A. 2002. DNA methylation and breast carcinogenesis. Oncogene 21:5462-82. Genomic rearrangements, deletions, amplifications, and point mutations of genes regulating cell growth, apoptosis and DNA repair are responsible for unregulated proliferation. Vogelstein B, Kinzler K W. 2004. Cancer genes and the pathways they control. Nat Med 10:789-99.
Alterations in oncogenes and tumor-suppressor genes also contribute to tumorigenesis. Davies H, Bignell G R, Cox C, Stephens P, Edkins S, Clegg S, Teague J, Woffendin H, Garnett M J, Bottomley W and others. 2002. Mutations of the BRAF gene in human cancer. Nature 417:949-54. Friedberg E C. 2003. DNA damage and repair. Nature 421:436-40. Nowell P C. 2002. Tumor progression: a brief historical perspective. Semin Cancer Biol 12:261-6. Santarosa M, Ashworth A. 2004. Haploinsufficiency for tumor suppressor genes: when you don't need to go all the way. Biochim Biophys Acta 1654:105-22.
Common targets for amplification and deletion include ERBB2, MYC, CDKN2A, PTEN, and SMAD4. Collins S, Groudine M. 1982. Amplification of endogenous myc-related DNA sequences in a human myeloid leukaemia cell line. Nature 298:679-81. Hahn S A, Schutte M, Hoque A T, Moskaluk C A, da Costa L T, Rozenblum E, Weinstein C L, Fischer A, Yeo C J, Hruban R H and others. 1996. DPC4, a candidate tumor suppressor gene at human chromosome 18q21.1. Science 271:350-3. Kamb A, Gruis N A, Weaver-Feldhaus J, Liu Q, Harshman K, Tavtigian S V, Stockert E, Day R S, 3rd, Johnson B E, Skolnick M H. 1994. A cell cycle regulator potentially involved in genesis of many tumor types. Science 264:436-40. Li J, Yen C, Liaw D, Podsypanina K, Bose S, Wang S I, Puc J, Miliaresis C, Rodgers L, McCombie R and others. 1997. PTEN, a putative protein tyrosine phosphatase gene mutated in human brain, breast, and prostate cancer. Science 275:1943-7. Slamon D J, Clark G M, Wong S G, Levin W J, Ullrich A, McGuire W L. 1987. Human breast cancer: correlation of relapse and survival with amplification of the HER-2/neu oncogene. Science 235:177-82. Steck P A, Pershouse M A, Jasser S A, Yung W K, Lin H, Ligon A H, Langford L A, Baumgard M L, Nattier T, Davis T and others. 1997. Identification of a candidate tumor suppressor gene, MMAC1, at chromosome 10q23.3 that is mutated in multiple advanced cancers. Nat Genet 15:356-62.
In breast tumors, genomic regions that are consistently abnormal have been termed “saw-tooth” and “firestorm regions” because they possess the highest frequencies of gains and losses of genomic sequences (Hicks, et al., 2006). However, investigation of genes with little or no variation in copy number or expression has not been a focus of cancer studies, even though they may also contribute to maintenance of the tumor phenotype.